NOD2 is highly expressed in Behcet disease with pulmonary manifestations

Background: Excessive Th1 cells and TLRs functions are involved in the pathogenesis of Behcet's disease (BD) in response to bacterial antigens. NOD2, an intracellular pathogen recognition sensor, modulates innate defence to muropeptides derived from various bacterial species. To further define a role for NOD2 in BD, we analysed NOD2 transcriptional responses in BAL-MNC from BD patients with pulmonary manifestations. Methods: We analysed NOD1, NOD2, T-bet and TLRs mRNA expression with real-time polymerase chain-reaction in BAL cells obtained from 23 BD patients with pulmonary manifestations and their matched controls. Results: We found that NOD2 mRNA expression was highly up-regulated in BAL cells from BD and sarcoidosis patients compared to healthy control group (P = 0.001). In BD patients, significant correlation was found between NOD2 and T-bet mRNA expression (r = 0.602; P = 0.0009). In BAL from BD patients, NOD2 and T-bet mRNA expression were significantly correlated with BAL-lymphocytes (r = 0.485, P = 0.010; r = 0684, P = 0.0001 respectively). NOD2 in BD was also correlated with TLR 2(r = 0.444; P = 0.021) and TLR 4 (r = 0.574; P = 0.001) mRNA expression. Conclusion: Our results indicate that BAL-MNC from BD patients expressed NOD2 as a result of lung inflammation. TLRs and NOD2 synergize for the induction of proinflammatory cytokines. BAL inflammatory cells showed an increased Th1 situation as indicated by increased T-bet mRNA expression.